Researchers achieve high-rate and stable ammonia electrosynthesis from nitrate

Ammonia (NH₃) is traditionally produced through the energy-intensive Haber-Bosch process which converts nitrogen (N₂) and hydrogen (H₂) into NH₃ at high temperatures (400–500℃) and pressures (10–30 MPa). This process consumes 1%–2% of global energy and contributes about 1% of global CO₂ emissions.

Electrocatalytic nitrate reduction reaction (NO₃⁻RR) is a renewable energy-driven process that uses nitrate (NO₃⁻) from wastewater as N₂ source and water as H₂ source. This low-carbon route provides a sustainable solution for NH₃ synthesis under mild conditions. However, its practical application has been limited by unsatisfactory electrocatalytic activity and poor long-term stability.

A research team led by Prof. Gao Dunfeng, Prof. Wang Guoxiong, and Prof. Bao Xinhe from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS), by introducing an amorphous/crystalline dual-phase Cu foam electrode with high performance, achieved high-rate and stable NH₃ electrosynthesis from NO₃⁻. The study was published in Nature Communications.

Researchers fabricated the electrode by thermal annealing commercial Cu foam in air, creating a unique dual-phase structure. With an alkaline membrane electrode assembly electrolyzer, they achieved an NH₃ partial current density of 3.33 A/cm² and an NH₃ formation rate of 15.5 mmol/h/cm² at a cell voltage of just 2.6 V. The electrode maintained stable NH₃ production with a Faradaic efficiency of around 90% at an applied current density of 1.5 A/cm² over 300 hours.

Furthermore, researchers identified that the stable amorphous Cu domains present during the reaction are key to the outstanding catalytic performance. This integrated Cu foam electrode performs better than conventional power electrodes, and the preparation protocols are facile and easy to scale up. In a scale-up demonstration using a 100 cm² electrode, an NH₃ formation rate of up to 11.9 g/h at an applied current of 160 A was achieved.

“Our work also underscores the importance of stabilizing metastable amorphous structures for improving electrocatalytic reactivity and long-term stability,” said Prof. Wang.